A comparative study of catalyst deactivation in integrated two-stage direct coal liquefaction processes

Abstract

Catalyst samples from Wilsonville runs 242, 246, 247, and 248 have been characterized and tested for hydrodesulfurization activity in order to determine the effects of different process configurations and coals on the causes and rates of deactivation. Initial rapid decreases in activity were caused by the accumulation of carbonaceous deposits within the catalyst. Variations in the amount of deposition were due to the process configuration but not the coal type. The process configuration with the most preasphaltenes and unconverted coal in the hydrotreater feed yielded the greatest buildup of carbonaceous deposits and the most deactivation. After the initial high losses, the activities continued to decrease with catalyst age due to the accumulation of contaminant metals in the catalyst. The rates of contaminant metals buildup varied significantly from run to run. Deactivation by carbonaceous deposits and contaminant metals was due to both poisoning of active sites and decreases in effective diffusivities. In addition, sintering of the active metals was observed in the aged catalysts.

Direct liquefaction techniques on lignite coal: A review

“…Suitable sufficiently cheap catalysts are mainly iron-based (hydroxide, sulfate, pyrite), although other metals and their oxides, halides, or sulfides have been used [57]. To minimize the catalyst deactivation, it is desirable to use coals containing low concentrations of nitrogen and sulfur [56] and to remove inorganic components and other impurities prior to the reaction [58]. The presence of a hydrogen donor solvent assists in reducing the required residence time [59] and the temperature required to obtain high yields of small-molecular-weight products.…”

Studies of coal reactivity for direct liquefaction

“…The reactive free radicals formed in the dissolution step of coal liquefaction may be stabilized by reaction either with hydrogen, primarily from a hydroaromatic donor molecule or with another aryl free radical. While reaction with hydrogen leads to the desired low molecular weight products, reaction with an aryl free radical produces undesirable refractory high molecular weight material responsible for reduced yields of liquids, catalyst deactivation (14) and problems with process operability, for example preheater plugging (15).…”

Novel supports for coal liquefaction catalysts

“…Concentrations of up to (and sometimes exceeding) five weight percent a!e common. The analysis of spent catalysts from the Wilsonville facility revealed that the penetration depth can be quite substantial (4).…”